Crystalline microporous materials.
Zeolites are crystalline microporous materials of varying compositions, characterized by a crystalline network of TO4 tetrahedrons (wherein T represents atoms in a formal oxidation state of +3 or +4 as for example Si, Ti, Al, Ge, B, Ga, . . . ) which share all their vertices, giving rise to a tridimensional structure containing channels and/or cavities of molecular dimensions. When some of the T atoms present an oxidation state lower than +4, the thus formed crystalline network presents negative charges that are compensated by the presence of organic or inorganic cations in the channels or cavities. In said channels, there may also be housed organic molecules and H2O for which reason, in a general manner, the chemical composition of zeolites may be represented by the following empirical formula:
x(M1/nXO2):yYO2:zR:wH2O 
wherein M is one or several organic or inorganic cations of charge +n; X is one or several trivalent elements; Y is one or several tetravalent elements, generally Si; R is one or several organic substances. Although the nature of M, X, Y and R and the values of x, y, z and w may, in general, be varied by means of postsynthesis treatments, the chemical composition of a zeolite (as synthesized or after its calcination) has a characteristic range for each zeolite and for the method by which it has been obtained.
On the other hand, a zeolite is further characterized by it crystalline structure which defines a system of channels and cavities that gives rise to a specific X-ray diffraction pattern. In this manner, zeolites differ in respect of each other by its range of chemical composition plus their X-ray diffraction pattern. Both characteristics (crystalline structure and chemical composition) further determine the physical-chemical properties of each zeolite and its applicability in different industrial processes.
The present invention refers to a crystalline microporous material of zeolitic nature, named ITQ-10, to a method for obtaining it and to the uses thereof.
Such a material is characterized by its chemical composition and by its X-ray diffraction pattern. In its anhydrous and calcinared form, the composition of ITQ-10 can be represented by means of the following empirical formula
x(M1/nXO2):yYO2:SiO2 
wherein x has a value lower than 0.1 whereby it may be equal to zero; y has a value lower than 0.1 and may as well be equal to zero; M is H+ or an inorganic cation of a charge +n; X is a chemical element with oxidation state +3 (as for example Al, Ga, B, Cr) and Y is a chemical element with oxidation state +4 (as for example Ti, Ge, V). When x=0 and y=0, the material may be described as a new polymorphous form of silica (SiO2) being characterized by its microporous character. In a preferred form of the present invention, in calcinated and anhydrous state, ITQ-10 has the composition
x(HXO2):SiO2 
wherein X is a trivalent element and x has a value lower than 0.1 and may be equal to zero, in which case the material may be described by means of the formula SiO2. However, depending on the method of synthesis and on its calcination or subsequent treatments, the presence of defects in the crystalline network manifesting themselves in the presence of Sixe2x80x94OH groups (silanols) is possible. These defects have not been included in the previous empiric formulas. In a preferred form of the invention ITQ-10 only has a very low concentration of this kind of defects (silanol concentration lower than 15% in respect of the whole amount of Si atoms, preferably lower than 6%, measured by 29Si nuclear magnetic resonance spectroscopy in magic angle).
The X-ray diffraction pattern of ITQ-10 as synthesized by the powder method using a set divergence split is characterized by the following values of interplanar spacings (d) and relative intensities (I/I0):
The positions, widths and relative intensities of the peaks depend to a certain extent on the chemical composition of the material (the pattern represented in Table I refers only to materials the network of which is composed exclusively of silicon oxide, SiO2 or and synthesized using a quaternary ammonium cation as structure directing agent). Furthermore, the calcination gives rise to significant changes in the X-ray diffraction pattern, due to the elimination of organic compounds that have been retained in the pores of the zeolite during synthesis, so the diffraction pattern of calcinated ITQ-10 of the composition SiO2 is represented. In FIG. 1 there is shown the diffraction pattern of a sample of calcinated ITQ-10 of the composition SiO2.
From the viewpoint of chemical composition, ITQ-10 is characterized by having a (Si+Y)/X ratio higher than 10, wherein the element x may be constituted exclusively of Al, and due to its low concentration of connectivity defects ( less than 15%, preferably  less than 6%). Furthermore, ITQ-10 may be synthesized without Al, or another element with oxidation state +3 in which case ITQ-10 is a new polymorphous form of silica of a microporous nature.
The present invention also refers to the method of preparing ITQ-10. This comprises a thermal treatment at a temperature between 80 and 200xc2x0 C., preferably between 130 and 200xc2x0 C., of a reaction mixture containing a source of SiO2 (as for example tetraethylorthosilicate, colloidal silica, amorphous silica), an organic cation in the form of a hydroxide, preferably 1,4-diquinuclidinium butane dihydroxide (I), hydrofluoric acid and water. Alternatively, it is possible to use the organic cation in the form of a salt (as for example a halide, preferably chloride or bromide) and to replace the hydrofluoric acid by a fluorine salt, preferably NH4F. The reaction mixture is characterized by its relatively low pH, pH less than 12 preferably  less than 10, whereby it may also be neutral or slightly acid. 
Optionally, it is possible to add a source of another tetravalent Y and/or trivadent element X, preferably Ti or Al. The addition of this element may be made before heating the reaction mixture or at an intermediate time during said heating. On occasions, it may be convenient to furthermore introduce, at some stage of the preparation, ITQ-10 crystals (between 0.10 and 15% by weight in respect of the whole of inorganic acids, preferably between 0.05 and 5% by weight) as crystallization promoters (seeding). The composition of the reaction mixture corresponds to the general empirical formula
rR(OH)2:aHF:xX2O3:yYO2:SiO2:wH2O 
wherein X is one or several trivalent elements, preferably Al; Y is one or several tetravalent elements; R is an organic cation, preferably 1,4-diquinuclidinium butane; and the values r, a, x, y, and w are within the ranges
r=R(OH)2/SiO2=0.01-1.01 preferably 0.1-1.0
a=HF/SiO2=0.01-1.0, preferably 0.1-1.0
x=X2O3/SiO2=0-0.05
y=YO2/SiO2=0-0.1
w=H2O/SiO2=0-100, preferably 1-50, more preferably 1-15
The thermal treatment of the reaction mixture may be carried out in a static manner or with agitation of the mixture. Once crystallization has ended, the solid product is separated and dried. The subsequent calcination at temperatures between 400 and 650xc2x0 C., preferably between 450 and 600xc2x0 C., produces the decomposition of the organic residues that are occluded within the zeolite, and the exiting thereof and of the fluoride anion whereby the zeolitic channels are left free.
This method of synthesis of the zeolite ITQ-10 has the particularity that it does not require alkaline cations to be introduced into the reaction mixture. As a consequence thereof, R is the only cation that compensates network charges when the zeolite contains a trivalent element within its crystalline network. Thus, a simple calcination to decompose the organic cation leaves the zeolite in an acid form without the need to resort to processes of cationic exchange. Once calcinated, the material thus responds to the general formula
x(HXO2):yYO2:SiO2 
wherein x has a value lower than 0.1 whereby it may be equal to zero; y has a value lower than 0.1 and may also be equal to zero; X is a chemical element with oxidation status +3 and Y is a chemical element with oxidation state +4.